1. Field of the Invention
This invention relates to a high-temperature detecting apparatus for detecting the temperatures of a high-temperature fluid as high as 500.degree. to 1,200.degree. C, or more in particular to a high-temperature detecting apparatus suitable as an overheat alarm for an exhaust gas system of an automobile engine.
2. Description of the Prior Art
A conventional overheat alarm for an exhaust gas system of an automobile employs a high-temperature detecting apparatus including a combination of an electronic switching circuit and a high-temperature thermistor or a thermocouple. Such an apparatus includes a separate sensor section and a separate electronic circuit section and therefore its mounting and wiring on the car body are time-consuming work. In addition to this problem, the sensor is expensive. Also, various measures are required to be taken on the sensor and circuit sections for prevention of operating errors due to water absorption or electric noise, thus further complicating the construction of the apparatus. This unavoidably increases the overall cost of the apparatus and makes it difficult to meet the requirements for high reliability and low cost of the apparatus for use with the automobile.